Wednesday, July 31, 2013

The title of this report is misleading, because one doesn't learn quantum physics (or any science for that matter) like this. Rather, one is learning ABOUT quantum physics. There is a difference here, and I've mentioned this quite a while back in context with my take on the many pop-science books out there.

While learning about science should be highly encouraged, especially among the general public, we should never mistaken it as learning science, because this practice provides information only at the superficial level.

Tuesday, July 30, 2013

See, this is essentially what is different between this blog, and the outlandish stuff they have elsewhere that tries to capture people's attention by drawing onto something that's improbable.

Last week, I highlighted a paper in PRL on the estimate made on the lifetime of photons based on current measurements. This upper limit also is related directly to the upper limit on the mass of photons, if any. In that blog post, I tried to highlight what is well-known and well-established, rather than try to make extrapolations on things that are still up in the air.

But that is not what is done here. This news report, also reviewing the same publication, decides to go with a different route, which is highlighting the speculative, attention-grabbing possibility, no matter how remote, how unlikely, and how improbable it might be. It focuses a lot on the minute possibility of photon decay, and decaying into "lighter" produced that could travel faster than the photons themselves.

If photons do break down, the results of such decay must be even lighter
particles, ones that would travel even faster than photons. Assuming
photons have mass, "there is only one particle we know from the Standard
Model of particle physics that might be even lighter — the lightest of
the three neutrinos," Heeck said.

It is sad that, rather than emphasizing the result that was published, news account on something like this would venture into citing remote possibilities and highly speculative conjectures. The result itself got buried. Rather, an improbable consequence of a possible outcome is the one that was brought to the forefront! This is a shameful attempt at sensationalizing a result! It is no different than the sensational front page news from supermarket tabloids.

The team chose dysprosium because it has a pair of closely-spaced
energy states that involve orbitals where electrons travel at very
different speeds. Because of this speed difference, a change in the
electron’s kinetic energy due to a change in the atom’s orientation
would affect the two states very differently. The researchers
illuminated a beam of dysprosium atoms with two laser beams to excite
them to state B (via another state) and then drove the transition to A
with a precisely calibrated microwave beam. To measure the transition
energy, they found the microwave frequency most effective at driving the
transition. The team repeated the experiment many times over a period
from 2010 to 2012.

The orbitals of the atoms were oriented to some extent by the
polarization of the exciting laser beams. So if the electrons’ kinetic
energy depended on their direction of motion, the team would have seen a
daily oscillation in the transition energy from the earth’s rotation.
Similarly, if there were any effect from the earth’s position in the
sun’s gravitational field (violating local position invariance), there
would have been an annual oscillation.

There are many different ways to violate Lorentz invariance, so
researchers in the field have developed a standard set of parameters to
characterize different types of violations. Hohensee and his colleagues
measured eight of the nine parameters that describe any dependence of
the electron’s maximum attainable speed on the speed and direction of
the lab’s reference frame. They significantly improved limits from
previous experiments for four of them, one by a factor of 10. Their new
limits on local position invariance for electrons are 160 times more
precise than previous ones.

Friday, July 26, 2013

While the accident in Spain is certainly a tragedy, it is also an opportunity to examine the physics involved for us to understand a bit more of a possible cause of the accident. This article in The New Yorker has a simple enough description of it that anyone without any mathematics or science degree can understand. It tries to explain why there is speed requirement or limit of curved tracks.

One of those forces is centrifugal (“to flee from the center”) force,
the inertia that makes a body on a curved path want to continue outward
in a straight line. It’s what keeps passengers in their seats on a
looping roller coaster and throws unsecured kids off carousels.
Centrifugal force is a function of the square of the train’s velocity
divided by the radius of the curve; the smaller and tighter the curve,
or the faster the train, the greater the centrifugal force. As it
increases, more and more of the weight of the train is transferred to
the wheels on the outermost edge of the track, something even the
best-built trains have trouble coping with. That’s where the concepts of
minimum curve radius and super-elevation, or banking, come in.

Banked curves, in which the outer edge of the track is higher than
the inner edge, balance the load on the train’s suspension. Since
gravity pulls a train downward and centrifugal force pulls it outward, a
track banked at just the right angle can spread the forces more evenly
between a train’s inner and outer wheels, and help to keep it on the
track.

But banking the tracks isn’t a cure-all—a passenger train can tilt
only so far before people fall out of their seats. So the minimum curve
radius comes into play. Imagine that a curved portion of track is
actually running along the outer edge of a large circle. How big must
that circle be to insure that a train’s centrifugal force can be managed
with only a reasonable amount of banking?

It is interesting to note that this is the type of question that we deal with in first year intro physics.

Wednesday, July 24, 2013

I see questions on the mass of photon a lot on online forums. The idea that a photon has a mass has numerous implications, including a non-zero longitudinal polarization. Another consequence is that a photon having a mass is not stable and will eventually decay. Thus, it should have a lifetime.

For a photon to decay, it must have a mass—otherwise there’d be
nothing lighter for it to decay into. A photon with nonzero mass is not
ruled out by theory, but experiments with electric and magnetic fields
constrain the mass to less than 10−54
kilograms. Heeck assumed this upper limit and worked through a generic
model in which photons decay into even lighter particles, which could
potentially be neutrinos or some more exotic particles.

As a constraint, Heeck considered the CMB, the relic emission
from the hot, opaque plasma that persisted for several hundred thousand
years after the big bang. The CMB spectrum matches very closely a
perfect blackbody, which implies very few, if any, of the CMB photons
decayed on their 13 billion year journey. Heeck calculated that the minimum lifetime is 3
years in the photon’s rest frame. This might seem ridiculously small,
but the photons are extremely relativistic. When time dilation is taken
into account, a visible wavelength photon in our reference frame would
be stable for 1018 years or more.

In other words, it is horribly longer than the age of our universe by many orders of magnitude! I'd say the odds of observing such a decay is zero.

Tuesday, July 23, 2013

Before we start, let me emphasize that I'm a man, but I've been involved in promoting women participation in science, and especially physics, for years. Anyone who has followed this blog would have read several items on this issue, and also my activities in this area to promote women in science. I definitely think that there is an under-representation of women in physics, and one of the ways to improve that is to make the field more enticing and more familiar to them, both in terms of the subject matter, and the working condition.

Now, having said that, you know what's coming next is not going to be pretty. This is a news article that reports on a recent statistical analysis/modeling done by the American Institute of Physics. It aimed to address that fact that fully 1/3 of the physics departments here in the US do not have a single female faculty member. But one shouldn't stop there, because the statistics included schools with small number of faculty members (often less than 10), and these tend to be the schools that do not have any female faculty members.

The AIP ran a simulation that takes into account the number of available female faculty members and the available positions, and came out with the conclusion that the lack of female faculty members in these departments is consistent with the statistical distribution, and not due to any inherent bias.

A new report
from the American Institute of Physics -- based on simulation analysis
-- concludes that the large number of departments without a single woman
is to be expected and is not the result of discrimination. Some experts
on women and science, however, disagree.

The institute's report says that there are two factors that explain
the distribution of women among departments: the size of departments and
the total number of female faculty members available. There are many
departments with only two or three physics faculty members, the report
notes. So "it is unlikely that these departments will have a woman among
the faculty because the overall representation of women among all
physics faculty members is low," the report adds.

To put it simply, say that you have 100 balls. On the table, you have many compartments of various sizes, some able to contain 20 balls, while others are big enough to have only 2 balls. If you toss those 100 balls up in the air and let them land randomly into those compartments, the argument here says that naturally, the smaller compartments will have a higher probability to end up with having NO balls.

Whether one buys into the parameters set up for the simulation is another matter. But taken at face value, I don't see anything wrong with this. It is certainly a first attempt at trying to figure out if the lack of any female faculty members in these small departments are due to some inherent bias, or simply out of statistics. It is a scientifically valid methodology to START and investigate an issue. Now the next logical step is to re-examine if the parameters used are valid, or accurate. Maybe some of the assumptions used are debatable, etc., and thus, the simulation should be tweaked.

What annoys me is the response being given to this study. I certainly expect disagreement with the conclusion, but the counter-argument that has been given is purely speculative!

Janet Bandows Koster, executive director and CEO of the Association
for Women in Science, said via e-mail that the report "a
disappointment."

She urged physicists to study the concept of "implicit bias," which
she said might have something to do with the pool of women in the
discipline. "We know that most people are reluctant to accept that they
are biased, and scientists in particular pride themselves on their
impartiality. Yet scientists are humans raised in societies, and thus
are subject to collective messages that suggest men are suited to
science because they are independent and analytical whereas women are
better suited to care-giving and cooperative enterprises."

It's too easy, she said, to focus only on the relatively small number
of women in the field. "Inferring there is no hiring bias because the
'n' is so small for female faculty is essentially like granting a papal
indulgence to physics departments across the country," she said.

I'm sorry, but that is stupid! You are countering a statistical analysis with nothing more than a speculative fishing expedition! That's like saying you don't agree with Special Relativity because you don't like the look of the equation!

And no one here is saying that there is no hiring bias. A statistical analysis such as this can't come to such conclusion. What it does say is that the lack of female faculty members in 1/3 of the physics depts. cannot be attributed to gender bias as the main factor, because statistical analysis alone can account for that observation! As scientists, we need to know what statistics say, and what they don't!

The PROPER way to counter something like this is to look at the validity of the parameter used, to see if the model is accurate, and to show where it might have missed something, NOT to simply insinuate that there are biases. For someone who is supposed to represent an association of women in SCIENCE, she sure used a lot of hand-waving, unsupported argument to counter a scientifically-derived conclusion.

In the paper, the trio critique an application of what psychologists call the "positivity ratio"
-- the ratio of a person's positive feelings to his/her negative
feelings. In 2005, two psychologists wrote that people "flourish" if the
ratio meets or exceeds 2.9 -- that is, if positive emotions occur at
least three times as often as negative ones. A pretty intuitive concept
in the abstract sense, but one Sokal and his co-authors say cannot be
described by the equations the psychologists borrowed from physics.

Sunday, July 21, 2013

Then again, perhaps it is not surprising that so many physicists wind up
working in finance. After all, they are good at using mathematics to
solve real-world problems and the money is good. There is more to it
than that though. There are mathematical links between physics and
finance that go back at least to 1900, when Frenchman Louis Bachelier
wrote his Theory of Speculation, in which he used the
mathematics of a random walk to analyse fluctuations on the Paris stock
exchange. Five years later, the same ideas were used by a young Albert
Einstein to explain why pollen grains zigzag when they are suspended in
water. His explanation invoked the idea that very large numbers of tiny
molecules, much smaller than the pollen grains, are responsible for
kicking the grains around. This was a crucial insight and provided one
of the earliest convincing confirmations of the existence of atoms. To
make the parallel with the financial markets, we might say that stock
prices are kicked around by myriad unknown factors in the marketplace.
Today, these ideas have been developed into a means of computing the
value of sophisticated financial instruments and the management of risk.

Now, I'm skeptical with the first assumption that there are physicists who "gravitate" towards a job in finance. I am not sure to what extent these people AIMED for such a job, or rather if they took it due to other circumstances. Would they have taken it if they had other jobs in physics that pay close to what they would be making? Did they graduate with the intention of take such jobs in finance?

Furthermore, I've mentioned a few articles in which these theoretical model in finance and areas dealing with social and human interactions and activities (what is often called as psychophysics) are being called into question.

In any case, this is an article that covers what is going on in the UK, and it doesn't look to be that much different than what is happening here in the US.

Friday, July 19, 2013

Again, if this was another obscure, backwoods article, I wouldn't give a hoot. But this comes in with Scientific American tags! I do not know in what capacity this is part of Scientific American, but they ought to be ashamed of themselves to be associated with this type of garbage.

This article was written by a "Clarissa Ai Ling Lee". A search turns info that this is a Ph.D candidate at Duke University, majoring in Literature, and specializing in "..... in science and technology studies and comparative media
studies."

There are so many convoluted, metaphysically-injected theme, or outright mistakes, that one just doesn't know where to start. For example:

In our three-dimensional world (even it we count time, that merely
allows the curvature or space to be accounted for, and not much else),

Holy cow! Is she that ignorant, and is actually proud to share it with the world? I suppose those time-reversal symmetry (or lack of it) events are of no use. After all, we didn't use time in there just merely to allow for the curvature of space! Unbelievable!

But it gets better...

Cosmic rays, as high-energy charged particles, are sets of naturally
occurring particles found through the process of atmospheric nuclei
decay.

Now this is utterly wrong. High energy cosmic rays especially, a non-terrestrial. It originates elsewhere in the universe. So it definitely is not a produced of "atmospheric nuclei decay". Even a quick search on Wikipedia can correct that! How lazy can one get?

And if you can stomach it, here a winner when she attempts to describe beta decay:

According to the law of conservation, the disintegration of neutron
should produce equal part electrons and equal part protons, but this was
found not to be the case. Therefore, Enrico Fermi named it for a
particle which is supposed to exhibit zero mass and zero charge (a sort
of 'virtual' particle at that time) so as to counteract the 'shortfall'
that would have resulted from the proton and electron not being
consistently emitted as a 'neutrino.'

Did you have to rub your eyes and read that twice?

A beta decay produces EQUAL amount of proton and electron. There was never a problem with charge conservation. It was a problem of spin/momentum conservation!

And oh, she has picked an area we should study:

They want to know how understanding a specific property of strong
interaction at the subatomic level can help explain why so much of our
universe is constituted of dark matter.

Bet you didn't know that, did you, that the strong interaction, at the subatomic level, no less, can help explain our dark matter. Yes sir!

The rest of the article, if you have the patience to read it, is a mumbo-jumbo of words with a generous dose of meta-physical flavor (a very popular trick) and enough word salad that it makes it difficult to be falsified and comprehended.

And aren't we glad that this is just Part 1! Can't wait on what other bastardization that is in store next!

Thursday, July 18, 2013

I've read the "press release" of this work, but only had a quick
glance at the paper. But that should not stop you from having a look at
it.

This activity for elementary/primary level education is meant to give a rather visual representation
of the concept of energy, the ability of energy to transform from one
form into another, and the conservation of energy principle.

In the current study, the researchers report their ongoing
examination of an activity that they have created, called "Energy
Theater." Energy Theater is specifically designed to help learners
visualize energy and how it dynamically changes form and location. In
Energy Theater, learners (K-12 science teachers in this study) each play
the role of one "chunk" of energy, and indicate with hand gestures what
form that energy has (e.g., chemical, motion, gravitational, thermal).
Different objects are represented by loops of rope on the ground, and
learners can move from object to object, demonstrating energy moving
between those objects. While energy is not actually a material
substance, this metaphor can help learners think about how a fixed
amount of energy can flow between different objects.

For example,
the group may be given the problem of, "Show what happens when a hand
pushes a box across a table." Participants would first stand in the area
representing the hand, making the gesture for "chemical energy." One by
one, they would move to the area representing the box, changing their
gesture to "energy of motion." Other scenarios might include how energy
flows when an incandescent light bulb is turned on. The group must work
together to decide how the "theater" will play out for a particular
situation, making complicated decisions about just where and when the
energy will flow and take different forms.

It
sounds rather convoluted to me, but that is probably because I haven't
had the chance to actually see it. Maybe something like this can sink in
easier with students at that age and level.

Advances in this field of storing light have been astounding. It was only a few years ago that we had the amazing accomplishment of light being stopped and then "played back" out of Lene Hau's lab. And there have been more advances since then (read here). Now comes this latest paper (free access to the actual paper is available at that link).

There are two major accomplishment that are notable with this one:

1. They managed to store light and all of its coherent information for more than a minute, and

2. They are using a solid state medium, rather than atomic gasses, which will make this more viable for storing quantum information.

While solid-state devices would be preferable for applications, stopping
light in solids is more challenging: stronger interactions between
atoms and their environment severely limit the attainable coherence
times. But the effect has been demonstrated in a special class of
solids: crystals doped with rare-earth (RE) ions cooled at cryogenic temperatures. Since the atoms are naturally trapped
in the crystal, the motion of RE atoms is limited and the transitions
of interest take place between electronic levels (e.g., the 4f electrons of praseodymium) shielded from the crystal environment by outer full electronic shells (5s and 5p). This makes the coherence properties of these crystals exceptional.

Tuesday, July 16, 2013

Galina Weinstein has a rather nice article uploaded on arXiv recently on the history of the "light quanta" per Einstein's 1905 paper. In particular, she explored why this issue, or rather, the "light complex" that Einstein mentioned in his photoelectric effect paper, was never included directly in his Special Relativity paper. Rather, there was an implication that SR's validity actually depends on the correctness of the photoelectric effect paper and the energy of the light quanta.

Note that in the article, Einstein clearly considered that it is the idea of the light quanta, and NOT Special Relativity, that was truly revolutionary. He thought that Special Relativity was simply an extension of classical electromagnetism.. This is the view that John Ridgen has also taken in proclaiming that it is the photoelectric effect that is a truly revolutionary idea, more so than Relativity (link requires free registration).

On Sept. 16, 1982, Neil Swartz, a computer scientist at CMU, posed a
physics problem to his computer science colleagues on the department’s
“bboard,” a form of early online message board similar to today’s
Facebook group. Bboard users often posted science puzzles for one
another to solve and had been discussing the riddle of whether a canary
could fly in an elevator during free fall.

Swartz presented a new scenario, which involved a lit candle mounted on an elevator wall and a drop of mercury on the floor.

“Because of a recent physics experiment, the leftmost elevator has
been contaminated with mercury,” Gayle wrote. “There is also some slight
fire damage. Decontamination should be complete by 08:00 Friday.”

Despite posts noting that the warning was meant in jest, some people
apparently took the notice at face value, believing a mercury spill had
actually taken place. Various bboard users began joking about different
symbols that could identify posts that weren’t meant to be serious.

Eventually, Scott Fahlman, then a computer science research assistant
professor, proposed using :-) for joke posts—or, given the
preponderance of joke posts, simply using :-( for serious ones.

There ya go! And there are still people who question the value of physics??!!

Wednesday, July 10, 2013

Many physics students, especially graduate students, would recognize that name. Merzbacher's QM text is one of the more popular texts being used at both the advanced undergraduate level and graduate level. This famous author and physicist passed away last month.

Ironically, the new molecular wires aren't made with magnetic
materials at all. Rather, their MR effect relies on the conductivity of
nonmagnetic organic
dye molecules called DXP, which the Italian automaker Ferrari once
used to give their roadsters their trademark red color. Unlike
conventional inorganic
metals in which electrons zip through a crystalline lattice, in
organics electrons must hop from one molecule to another, like pails of
water being passed
by a bucket brigade. To create a MR, material researchers need to
switch off that bucket brigade in the presence of a magnetic field.

In organic materials researchers do this with a little help from
quantum mechanics. A tenet of quantum mechanics called the Pauli
Exclusion Principle
states that no two fermions (particles in a family that includes
electrons) can occupy the same quantum state. If two electrons with the
same quantum state
try to hop onto the same DXP, they can't. The bucket brigade turns
off and resistance skyrockets.

Of course, we all know (don't we?) that this is the field that has been responsible for invention of computer magnetic storage disks, etc. So kids, this is another example of real-world, practical application of physics, and quantum mechanics in particular.

Thursday, July 04, 2013

This latest research was done by researchers at the Laboratoire Charles
Fabry (LCF) in Palaiseau and the University of Lille. "What we have done
here, for the first time to our knowledge, is to measure directly the
Van der Waals interaction between two single atoms that are located at a
controlled distance, chosen by the experimenter," says Thierry Lahaye,
who is part of the LCF team.

Controlling the distance between normal atoms – while measuring the
force between them – is extremely difficult because the relevant
distances are tiny. To get round this problem the team used Rydberg
atoms, which are much larger than normal atoms. Such atoms have one
electron in a highly excited state. This means that they have a very
large instantaneous dipole moment – and therefore should have very
strong Van der Waals interactions over relatively long distances. They
also have unique properties that allow them to be controlled with great
precision in the lab.